Single-crystal ingots of CdTe and Cd0,96Zn0.04Te 60–100 mm in diameter were grown by directional solidification using the self-seeding technique. The microstructure of the crystals was checked by optical microscopy, electron microscopy (TEM, SEM and EBIC), cathodoluminescence, and X-ray diffraction. It was found that crystal perfection depends to a large measure on the temperature schedule during Lpostgrowth crystal cooling: special caution should be exercised in the temperature interval including the polymorphous transformation. A direct relationship between optical and electronic properties on the one hand and crystal microstructure on the other hand was established.